In order to quantify and monitor inflow along the deepest 5,000 ft of a 45,000 ft extended-reach drilling (ERD) well, a (non-radioactive) permanent inflow tracer system was installed, sampled, and analyzed. The tracer technology was piloted as a supplementary downhole data source to the existing practice of intervention-based production logging due to current limitations of intervention accessibility. This application aided in assessing contribution of the lateral segment within a 1-md reservoir quality rock and determining clean-up efficiency.
The deployed lower completion is a 6⅝-in limited entry liner, segmented by packers with design specifically optimized for bullhead stimulation. To meet well objectives, the design of lower completion, along with placement of tracer carrier subs, was geometrically optimized based on expected flow streams. Final deployment included 3 externally vented tracer carrier subs per compartment with optimized spacing, each mounted with a chemically different tracer for both oil and water. A total of 21 distinct signature tracers were deployed per phase within the 7 compartments with compartment length ranging from 681 to 782 ft. In addition, liner is equipped with dissolvable plugged nozzles for efficient mud cake breaker displacement.
Upon activation, the well was flowed for 2 weeks at maximum rate for efficient clean-up before shutting it for 1 week for tracer concentration build up. The well was then flowed, and 106 samples were taken in a decreasing sampling frequency. A subset of 17 samples were selected for analysis – the collected samples were oil with no traces of water. Analysis of the tracer concentration with time showed the arrival of all 21 oil tracer signals and peaks, followed by a decreasing trend towards steady state levels. Results indicate that all reservoir zones contribute to oil production and that all zones have responded similarly in terms of the tracer profiles. This suggests a homogenous reservoir pressure drawdown across all zones. Furthermore, this indicates that reservoir zones cleaned-up efficiently and demonstrates effectiveness of an applied mud cake breaker displacement technique. The tracer results indicate minimum formation damage – in line with expectations, as the target area is a homogeneous 1-md rock quality with uniform reservoir pressure. Using the tracer data, a quantitative interpretation was performed, by use of the so-called flush out tracer transport model. The methodology was successful in determining relative flow contribution per traced zone. Results shows a uniform relative inflow contribution ranging from 4 to 6% per zone. The chemical inflow tracers were deployed in a well with world-record length of 6⅝-in lower completion at 29,243 ft, beyond current accessibility limits of rigless intervention. Also, the well is ranked 5th worldwide (as of time of this writing) in terms of longest well at 45,000 ft, thus making it a world-record in terms of the deepest deployment of chemical inflow tracers.